Developing system for electrostatic copying machine



Feb. 6, 1968 v. MARQUART ETAL 3,367,305

DEVELOPING SYSTEM FOR ELECTROSTATIC COPYING MACHINE 5 Sheets-Sheet l Filed Dec.

7 INVENTORS VERA/0N1. Maeauner 1968 v. L. MARQUART ETAL 3,367,305

DEVELOPING SYSTEM FOR ELECTROSTATIC COPYING MACHINE Filed Dec. 6, 1963 5 Sheets-Sheet 2 INVENTORS VERNON L Mam-we QT MARVIN W TEuTscH J K/RK 5W/6ERT QTTORMEYS Feb. 6, 1968 v. MARQUART ETAL 3,367,305

DEVELOPING SYSTEM FOR ELECTROSTATIC COPYING MACHINE Filed Dec. 6, 1963 5 Sheets-Sheet Z INVENTORS ERNONLMHRQUQQT MARV/N W TEUTSCH J KIRK SVV/GEPT 4 TTOPNEYS Feb. 6, 1968 v L. MARQUART ETAL DEVELOPING SYSTEM FOR ELECTROSTATIC COPYING MACHINE 5 Sheets-Sheet 4 Filed Dec. 6, 1963 INVENTORS VERNONL MQQ UAQT MHRV/N W. TEUTSCH QTTORMEYS Feb. 6, 1968 v. 1.. MARQUART ETAL DEVELOPING SYSTEM FOR ELECTROSTATIC COPYING MACHINE 5 Sheets-Sheet 5 Filed Dec. 6, 1963 INVENTQRS VERNON 1.. MHRQUHRT MARI/IN w. TEUTSCH' l]. K/RK SW/GERT I M! HTTORNEYS United States Patent DEVELOPING SYSTEM FOR ELECTROSTATIC COPYING MACHINE Vernon L. Marquart, Scottsdale, and Marvin W. Teutsch and J. Kirk Swigert, Phoenix, Ariz., assignors to Nuclear Corporation of America, Phoenix, Ariz., a corporation of Delaware Filed Dec. 6, 1963, Ser. No. 328,741 3 Claims. (Cl. 118612) Our invention relates to a developing system for an electrostatic copying machine and more particularly to a liquid developing system which produces a clean, sharp copy in a rapid and expeditious manner.

Various forms of copying machines are known in the prior art. One type of copying machine of the prior art subjects a sheet of copy paper carrying a photoconductive coating to the action of a charging system which causes the paper to assume a static charge. An image of the original to be copied is focused on the charged paper so that the charge leaks off in the relatively lighter areas of the image and is retained over the relatively darker areas. Thus, the exposed copy paper carries a latent electrostatic image of the original.

Following the operations described above, the sheet of copy paper carrying the latent electrostatic image is subjected to the action of particles of toner material which are attracted to the charged areas of the paper. Following this developing operation, the toner is set and owing to the fact that the toner particles are of a color which contrasts with the color of the copy paper, the developed copy is a reproduction of the original.

There are known in the prior art copying machines of the type described above which employ a dry toner system wherein the toner particles are mixed with a carrier and the mixture is applied to the paper carrying the electrostatic image. While machines of this type will produce copies, they are in many respects unsatisfactory. Copies produced by these machines have relatively poor resolution and may have an intolerable amount of background dirt. The very fine toner particles are ditficult to control and dirty the machine necessitating frequent cleaning. Moreover, relatively elaborate systems are required to ensure that the mixture is brought into contact with the entire area of the copy sheet. Relatively high heat is required to set the particles of toner on the paper.

We have invented a developing system for an electrostatic copying machine which overcomes the defects of developing systems of the prior art. Our system employs a liquid developer which permits copies to be developed in a rapid and expeditious manner by merely drying the sheet. Copies produced by our system are clean and have excellent resolution. Our system uses only the minimum amount of toner to develop a clean, clear copy on each operation of the machine. Our machine is so arranged that it can be carried about without danger of spilling the liquid developer.

One object of our invention is to provide a developing system for an electrostatic copying machine which employs a liquid developer.

Another object of our invention is to provide a developing system for an electrostatic copy machine which produces clean, clear copies.

A further object of our invention is to provide a developing system for an electrostatic copy machine which uses a minimum amount of toner for each copy produced.

Yet another object of our invention is to provide a liquid developing system which permits a copying machine incorporating the system to be carried without danger of spilling the developer.

7 3,367,305 Patented Feb. 6, 1968 Other and further objects of our invention will appear from the following description.

In general our invention contemplates the provision of a developing system for an electrostatic copying machine in which, upon each operation of the machine, liquid developer is pumped from an enclosed toner supply reservoir to a developer tank through which the charged copy paper passes. We provide our tank with a weir for regulating the filling of the tank to a relatively low level so that excess developer flows back to the reservoir.

In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIGURE 1 is a side elevation of an electrostatic copy ing machine including our improved developing system.

FIGURE 2 is a fragmentary sectional view of the electrostatic copying machine shown in FIGURE 1.

FIGURE 3 is a plan view of the liquid toner tank of our improved developing system.

FIGURE 4 is a sectional view of the tank shown in FIGURE 3 taken along the line 4-4 of FIGURE 3.

FIGURE 5 is a schematic view illustrating the copy paper transport assembly of our improved developer systern.

FIGURE 6 is a top plan of an electrostatic copying machine including our improved developing system with the cover removed.

Referring now to FIGURES 1 and 2 we have shown an overall view of one form of copy machine indicated generally by the reference character 10 incorporating our developing system. The machine 10 has a case bottom 12 having a baseplate 14 which supports the operating parts of the machine. The case includes a top 16 which fits onto the bottom 12.

Since many of the details of the machine 10 do not per se form a part of our invention, We will not describe the machine in detail. These details are shown and described in the copending application of Marvin Teutsch, Ser. No. 320,159, filed Oct. 30, 1963 for Electrostatic Copy Machine. As is described in detail in the copending application, in use of the machine 10 when the machine is turned on by means of a switch 11 or the like a sheet of copy paper from a supply carried by a tray 18 is fed by a feed roll 20 toward a charging wand assembly 22. When the sheet arrives at a predetermined position, the copy paper feed drive is interrupted and the machine is ready to receive an original to be copied. The original is inserted into the machine through a passage 24 toward an original transport system indicated generally by the reference character 26. The system 26 carries the original past a window 28 through which light from a source 29 is focused onto the original. After passing by the window, the original is carried throughout the rest of the transport system 26 and ultimately is returned to the user on a tray 30. Either a single copy or a plurality of copies may be made from the original.

As the original enters the transport system 26, it operates a switch 27 to restart the copy drive system to cause the copy paper to pass through the charging wand at which it receives an electrostatic charge. The copy paper transport system indicated generally by the reference character 32 carries the copy with its charged side down past a window 34. Light from lamp 29 causes an image of the original to pass to an optical system 36 which reflects the image to a mirror 38 which directs the image to another mirror 40 which translates the image to the copy paper passing over the window 34. The charge on the photoconductive coating, such as zinc oxide, on the paper leaks off over the relatively light areas of the image and is retained in the darker areas. Thus, after having passed by the window 34 the copy paper carries a latent electrostatic image of the original. System 32 then carries the paper upwardly and directs it into the developer system indicated generally by the reference character 42.

As will be explained more fully hereinbelow, as the copy carrying the latent electrostatic image passes through the system 42 it is treated with liquid developer and the charged areas pick up particles of toner to develop the latent image. The developed paper then passes through the fixing system indicated generally by the reference character 44 of the machine which fixes the developed image and delivers the copy to the user on a tray 45 carried by the cover 16.

Referring now to FIGURES 2 to of the drawings, we have illustrated the details of the transport system 32 and of our developer system 42. The transport system 32 comprises a belt 46 carried by respective driven rolls 48 and 50 and by an idler roll 52. A roll 54 permits the tension on belt 46 to be adjusted. All of the rolls 48, 50, 52 and 54 are supported between side plates 56, one of which is shown in FIGURE 2, and they are driven in a manner to be described hereinbelow. Respective rolls 58 and 60 of the transport system 32 are supported on plates 56. These rolls 58 and 60 carry the second belt 62 of the double-belt transport system 32. The system 32 so carries the copy paper that the latent electrostatic image is not smudged or erased. Preferably we form the belts 46 and 62 from a material such as Mylar, which is the registered trademark of E. I. du Pont de Nemours & Co. for a highly durable, transparent, water-repellent film of polyethylene terephthalate.

As the sheet of copy paper leaves the belt system 32, it enters the toner tank 64 of our system. Tank 64 may be cast from any suitable material such, for example, as plastic. It has side walls 66 and 68 provided with inclined slots 70 and 72 which receive rubber-covered hold-down rolls 74 and 76. Extensions 78 and 80 on the walls 66 and 68 have slots 82 and 84 which receive the squeeze rolls 86 and 88 of the developer system. A sheet of copy paper carrying the latent image passes downwardly into the tank 64 and through the hold-down rolls 74 and 76 and thence upwardly to the squeeze rolls 86 and 88.

We provide the surface of the tank 64 leading to holddown rolls 74 and 76 with a plurality of spaced ridges 71 extending in the direction of paper travel to facilitate passage of the paper through the tank. After passing through the rolls 74 and 76 the paper is guided upwardly by a pair of spaced guides 73 and 75 formed in the tank. We provide the guides 73 and 75 with ridges 77 extending in the direction of paper travel.

We space the hold-down rolls 74 and 76 by about 0.010 inch so that they do not squeeze the paper. The roll 88, as well as the rolls 74 and 76, is coated with rubber so that there will be no buildup thereon of toner particles which might smudge the copy. Squeeze roll 86 is steel and is continuously wiped by a wiper 90 carried by a splash shield 92 supported on the tank 64.

Tank 64 carries a fitting 94 which opens into a passage leading to an orifice 96 just below the hold-down roller 76 to supply liquid developer to the tank in a manner to be described. We form tank 64 with a weir 98 located between guide 75 and wall 68 so that the tank fills with liquid developer to a level determined by the height of the weir 98. Excess liquid flows over the weir into an outlet passage 100. We so size the orifice 96 as to permit the tank to fill to the level of the weir within about five seconds from the time the machine is turned on. The copy paper passes through the developer system 42 face up so that the image is not smeared as the paper rides over the bottom of the tank 64.

Our developer system includes a reservoir 104 disposed adjacent one of the sides of the bottom 12 of the case. A motor 106 carried by the reservoir 104 has a shaft 108 for driving the pump 110 of our machine. A

support rod 112 suspends a pump within the reservoir. A hose 114 connects the pump output to the fitting 94 on the tank 64 to supply fluid to the tank. A tube 116 connects the overflow passage fitting 117 to the reservoir 104. A screw boss 118 is provided to secure the tank cover.

It will readily be understood that we may employ any liquid developer known to the art. For example, the developer may be an emulsion consisting of immiscible fluid carrier and toner phases, the latter being composed of a suspension of developer particles in an insulating liquid. The toner particles are car-ried on the surface of globules of the fluid carrier phase. The liquid developer may be a dispersion of finely divided opaque particles such, for example, as carbon, colored resins and glass in an insulating liquid. It has also been suggested that nonflammable, nontoxic developers be provided. For example, trichloromonofluoromethane or trichlorotrifluoroethane are used with a coloring matter such as phthalocyanine blue and a fixture such as an alkyd resin. Any other suitable liquid developer can be used.

When it is necessary to replenish the supply of toner, a can containing toner is pushed into a funnel 120 on top of the tank. The refill cartridge is provided with a soft plastic end which is punctured by a knife 122 to release the toner and permit it to flow into the tank through an opening 124 at the base of the tank.

We provide our system with means for signalling when the supply of developer is below a predetermined level. A float 126 disposed within the tank is carried by a rod 128 slidably supported in a bracket 130 on the tank. A stop 132 limits the upward movement of the float. Rod 128 is connected to the actuating element 134 of a switch 136 adapted to be operated to signal the fact that the developer is below a predetermined level and requires replenishing.

After leaving the squeeze rolls 86 and 88 the developed copy passes to a transport system indicated generally by the reference character 138 comprising belts 140 which carry the copy between a pair of ducts 142 and 144, each having perforations 146 in their sides facing the paper to permit hot air to be directed onto the paper to fix the image. The developed copy carrying the fixed image finally passes to the delivery tray 45. A pipe 148 connected to the tube 114 taps some of the liquid being pumped to the tank 64 to produce a jet of liquid which constantly agitates the liquid toner in the reservoir to ensure that the suspended particles remain uniformly dispersed through the carrier.

Referring now to FIGURES 2 and 5, in FIGURE 5 we have schematically indicated the axes of the more important rolls of the transport systems by dot-dash lines. Our machine includes a drive motor 150 supported on the base 14 having a drive shaft 152 which drives a sprocket wheel 154 carrying a pitch chain 156. Chain 156 extends around an 'idler sprocket wheel 158 to the original transport system 26 in a manner more fully disclosed in the copending application referred to herein above. Chain 156 also drives a sprocket wheel 160 carried by a shaft 162 which support a gear 164. Gear 164 meshes with and drives gears 166 and 168 which drive rolls 50 and 48. Gears 166 and 168 drive pinions 170 and 172 on the nollers 58 and 60. A shaft 174 carries a sprocket wheel 176 driven by chain 156 and a gear 178 in engagement with a pinion 180 which drives one of the rolls 182 of the fixing transport system 138.

A pocket 184 outboard of the side 78 of the trough 64 supports a train of gears 186, 188, and 192 which provide a driving connection between gear 178 and a gear 194 which drives the lower hold-down roll 76. Gear 194 drives a gear 196 carried by the upper hold-down roll 74. A shaft 198 carries a sprocket wheel 200 driven by chain 156 and a gear 202 in engagement with another gear 204 on the input member of a clutch 206 adapted to be energized to couple gear 204 with the roller 20 which feeds the copy paper.

In operation of our developer system, when the machine is turned on motor 106 is energized to drive pump 110 to supply liquid developer through pipe 114 and orifice 96 to the tank 64. The tank begins to fill with liquid and when the liquid level rises to the height of the weir 98, the excess toner flows over the weir through passage 100 and through pipe 116 back to the reservoir. A portion of the liquid being pumped is tapped by pipe 148 to produce a jet of liquid within the reservoir which constantly agitates the supply of liquid to ensure that the particles of toner are dispersed throughout the liquid. Now as an original to be copied is fed to the machine, a piece of copy paper moves from the ready position through the charging wand and through the double-belt transport system 32 past window 34 to the reservoir 64. In this position the side of the paper carrying the latent image faces up. The sheet slides down along the bottom of the tank until it is picked up by the hold-down rolls 74 and 76. In the course of this movement particles of toner from the liquid developer in the trough adhere to the charged areas and the sheet rides upwardly on guides 73 and 75 and into the nip of the squeeze rolls 8'6 and 88. These rolls squeeze the copy so that it emerges from the rolls damp but not wet. The dam-p developed copy is then moved by belts 140 through the area between ducts 142 and 144 which blow hot air onto the paper. The dry copy is then delivered onto the tray 45.

As the supply of liquid developer is depleted, float 26 moves downwardly from its limit position determined by stop 132 until it operates switch 136 to produce a signal indicating that the supply is nearly exhausted. Then the operator pushes a replenishing cartridge into the funnel 120 until knife 122 punctures the cartridge and the toner flows through opening 124 into the tank 104.

It will be observed that the input orifice 96 is positioned adjacent the lowest portion of the developer tank 64. During the development operation, the pump 110 runs continuously. When the machine is stopped, the developer will drain through the orifice 96, through the tube 114 back into the reservoir 104.

It will be seen that we have accomplished the objects of our invention. We have provided a developing system for an electrostatic or other copy machine employing a liquid developer. Our system produces clean, clear copies. It uses a minimum amount of toner for each copy pro duced. A machine incorporating our system may be carried without danger of spilling the developer.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims.

It is further obvious that various changes may be made in details within the scope of our claims without departing from the s irit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention what we claim is:

1. Apparatus for developing a latent electrostatic image carried by a sheet of photoconductive copy material including in combination: a tray for holding fluid developer; means forming a weir in said tray; a reservoir containing a supply of liquid developer; means for supplying liquid developer from said reservoir to said tray at one side of said weir to provide fluid developer in said tray at the level of said weir; means including hold down rolls having a nip below said level for guiding copy material through said tray towards said weir; said weir forming means providing a surface having ribs extending in the direction of movement of said copy material for guiding said copy material from said nip to said weir; and means on the other side of said weir for returning fluid developer to said reservoir.

2. Apparatus as in claim 1 including a pair of squeeze rolls and means mounting said rolls adjacent said tray above said level.

3. Apparatus as in claim 1 in which said developer supplying means comprises a pump and means in communication with said pump for producing a jet of developer liquid whereby to agitate said developer in said reservoir.

References Cited UNITED STATES PATENTS 1,547,426 7 1925 Lewis 118-429 X 2,168,997 8/1939 Lankes et al. 118-429 X 2,279,166 4/1942 Hodil et al.

2,554,803 5/ 195 1 Wysocki.

2,676,119 4/1954 Constance 118429 X 2,739,567 3/1956 Jones et al. 118-429 2,875,094 2/1959 Bloem et al l18-602 X 2,991,753 7/1961 Dearsley 118-262 3,207,128 9/1965 Leavitt et a1 118-602 3,249,088 5/1966 Ostensen 118-637 3,299,787 1/1967 Kolb et al. 1.7 3,124,484 3/1964 Magnusson 95-1.7 X

FOREIGN PATENTS 938,349 10/ 196 3 Great Britain.

MORRIS KAPLAN, Primary Examiner.

E. C. BLUNK, Examiner. 

1. APPARATUS FOR DEVELOPING A LATENT ELECTROSTATIC IMAGE CARRIED BY A SHEET OF PHOTOCONDUCTIVE COPY MATERIAL INCLUDING IN COMBINATION: A TRAY FOR HOLDING FLUID DEVELOPER; MEANS FORMING A WEIR IN SAID TRAY; A RESERVOIR CONTAINING A SUPPLY OF LIQUID DEVELOPER; MEANS FOR SUPPLYING LIQUID DEVELOPER FROM SAID RESERVOIR TO SAID TRAY AT ONE SIDE OF SAID WEIR TO PROVIDE FLUID DEVELOPER IN SAID TRAY AT THE LEVEL OF SAID WEIR; MEANS INCLUDING HOLD DOWN ROLLS 